Method of detecting pbesence amd appboximate location of metallic



O 1930. i F. s. CHAPMAN Re. 17,844

METHOD OF DETECTING PRESENCE AND APPROXIMATE LOCATION OF METALLIC MASSES Original Filed Nov. 12, 1919 Infant);

fl 5/;e'nC ma n ject of my invention is Meet-21.1930

UNITED STATES- Re.'11,s44

mum cnzarm, OI IL'YWOOD, ILLINOIS III-HOD 01' DITBGTIFG PRESENCE up) Lrrnoxnurn Loos-non or mum Original Io. 1,564,910, dated December 8, 1925, Serial l'o. 857,431, fled llovember 12, 1919. Application" for reissue filed lbec'erllber 5, 1921. Serial No. 837,961.

My invention relates to wireless electric communication systems generally, and the ob- First, to provide an lmproved means for receiving wireless impulses from beneath the a ground or water-bod surfaces;

Second, to provi e an improved means whereby -Wireless electric impulses may received at the same time wireless electric im ulses are being sent;

'- produced by a low frequency source, a

'rd, to provide. an improved .means whereby the direction of travel of wireless electric impulses may be determined, thus providing means which may be used in the :art for other purposes; and

Fourth, to provide an improved method of detecting the presence and approximate lo cation of metallic masses or other electrical conducting or wireless-wave reflectingmasses.

By the terms wireless or radio as used herein, I mean to cover waves of any frequency, whether it be in the magnetic field e,- quency in the audio range, or up to the highest radio wave that may be produced.

I attain these objects by the apparatus shown in the accompanying drawings in which:

Fig. 1 shows a portion of a sending-receiving wireless station having a ground-wireless antenna and an aerial antenna; Fig. 2 is merely another view of that portion of Fig. 1

comprising the antennae ff, the function of Fig. 2 being to indicate that the antenna ff of Fig. 1 comprise two sets at right angles to each other; 3 shows two large loop antenna; for receiving purposes, part of the wire'thereof being shielded with iron or other suitable metal tubes. This loop system is in a balancedposition with regard to L, a wireless-wave-source representing the central part of the field surrounding A, Fig. 1; Fig. 4 is an enlarged detail of part of H, Fig. 3.

F ig. 1 is a drawing showing the aerial antenna A, the wireless electric. sending set B,

and a ground wire C leading fromB. C is divided-at D as shown. EE are variable resistances. ff are two branches of G. ff comprise what I term the ground antennas and 5 are to be connected to earth or, if used on the sea, are to be grounded by being attached to suitable electrodes submerged in the water.

G is a detector and M the receiver located in the receiving circuit p through de tector G and receiver M an ener by the battery S associated therewith. should be placed in the central or balanced position so that when current is flowing to ground fromff no current will flow through G.- This may be done by well known methods.

Under such conditions, impulses maylbe sent from the system and will not be heard in. receiver M. Wireless electric impulses, com-,- ing from beneath the ground and travelingparallel with ff will cause a current to flow 1n ff, the resistance EE forcing the said curfrom this station, as it will not act as a conductor of outgoin current. i

2 shows two ground antennae arranged at right angles to and crossing each other at the common central point, as shown, and joined at D to which is connected the wireless sending set B and aerial antenna A as in Fig. 1. With this, two messages may be received at the same time, ifithe direction from which they are coming be at right angles, or approximately so, with each other. 01'' the whole apparatus. may be movedon the position of D as a pivot until, for a 'ven set of impulses being received, no noise is heard in one receiver and the heaviest noisein the other. Thus the line of direction of the impulses under observation may be determined.

Fig. 3 shows two looped antennae lo cated some distance apart with a pair of wires connecting them" through the linereversing switch J I, are exposed wires -The-: apparatus formmg' part of the loo the continuation of which wires-enter H? H, which are iron tubs the contmuation'ofII, I and iusulatedfrenrthelattertoall {Tillie urposeof Histointercepttera'o ii'aves so the? they will not cutthrough the tulle-enclosed parts of I, I, so that no current will be induced in such enclosed part of I, I. Were all of the wire of the loop exposed, the

wireless waves would induce current in both sides of the loop, of approximately equal but the current from one side of e loop would be in a direction to oppose that from the other, and both would be somewhat'neutralized, and hence would be somewhat inoperative as regards the receiver. .But by enclosing part of I, I in the tubes as -drown, a lender noise will be heard in the receiver and thus meshages may be better re-- g9 ceived. By adding large numbers of turns to the loop, this may be greatly increased. This action of the em as shown depends, however, on the position of J. If it be closed in one A, i looped antenna will coincide in direction that from the other, and the eflect be 'to boost the voltage and thus increase the efliciency. But, if J be thrown to the other tion, the two looped ac will buch iach other, and if both are at an equal distance from the wirelem source, silence in. the receiver will result.

Therefore, if L be a wireless wave source, (such as A and B, Fig. 1), separat- 85 ed from and at an approximately equal distance from both of the looped antennae, it may be worked and not heard in the re.- -'ceiver, if J be inthe bucking position. It may be dificult to absolute silence, but

' at least the sound w1ll be greatly reduced.-

- But another set'of wireless impulses, their source being further from one of the looped antennae than the other and not in a direction parallel to 11 may be heard in the re- "ceiver and not interfered with by L.

Impulses from L may cause induced impulses or reflected waves to come 1 from a nearby metal mass and these induced impulses, cutting through the looped an- 150 terms; may cause a. noise in thereceiver,

and thus indicate the presence of an otherwise hidden metal mass. In this case, all "the apparatus shown in Fig. 3 should be mounted on the same movable base, so that action L will always be at an equal distance from both looped antennae. By

re 1' maneuvering, the metal mass may be And tially this same action and result ma be had with Fig. 1.

own herein is also described, and claimed in'my application for patent dated as filed May 7 1921, Serial No.

467,782, communication system,

method of operating only being claimed '0: herein.

position, the output from one of the Fig. 4 shows an enlarged detail of H with its insulating part K separating I from H.

The method of operation is. as follows:

The system is first balanced in a location I corresponding in time and duration thereto is heard in any of the receivers M, it indicates the rescnce of a metal mass.

This noise may be first heard in any of the antennae, and if not in the apparatus covered by Fig. 3, there should be a change of direction of the ship until it is heard in M Fig. 3. The ship is then maneuvered in all possible directions and preferably over as small an area as possible until the noise in M, Fig. 3,

ceases or diminishes with comparative suddenness. The ship is then in the same'manner as before placed at right angles to the just-found silent position, and if the silence in M, Fig. 3 is still maintained, the ship is over the searched-for metal mass. If not, fur- V ther maneuvering of the ship\m be carried' on until the suddenly-arrived at silence.

or diminished reception ismaintained in M,

Fig. 3 in all positions of the ship. Thus the general line of direction between the ship and the metal mass may be determined as also the approximate location thereof.

When the metal mass to be located is beneath the ground, instead of beneath the surface of the sea, the apparatus maybe transported from placetoplace on the earths surface in the same mannerthat the ship was maneuvered in the above described operation.

By the expression balancing out or balancing asused herein in connection with the turning or moving of a receiving loop antenna so that the direction of wave travel may be found, I mean the ceasing or diminishing of reception, caused by two electric currents set up in the said loop antenna in such a way -minimum reception, which will be adequate for the purposes of this method. In practical operation of this balancing method, the loop Ill antenna of a recei set is usually turned on its vertical axis uring reception until reception ceases, or a point of minimum rece tion is reached.

I here are two distinct forms of balancing simultaneously utilized in this method. First, in each loop the current induced in one side of the loop is opposed to the current in duced in the opposite side by plane of the loop at right ang es to the rec sitio the tion of reception of the waves. 'Secondly, the two loops are balanced against one another by opposing the currents induced in each' loop, or the manifestations thereof,

against one another. In the apparatus .here disclosed'by way of example, this is accomplished by the reversing switch J Iclainiz V a 1. The method of deter'inining the general line of direction between a given position and a metal or other mass capable of returning radio waves which consists in propa gating radio waves, intercepting and translating reflex radio waves, andthen balancing out the said reflex radio waves or waves'resulting therefrom. v. I o 2. The method ofdeterminingthe location of a metalor other mass capable'of returning radio waves which consists in propagating radio waves, intercepting and translating reflex radio waves, determining" the gen'- waves therefrom at intervals, intercepting and translating reflex radio waves and increasing the manifestations of said waves by means of additional currents until said interception and translation ceases or reaches the minimum obtainable for that location, changing the direction of movement of the radio propagating device and again intercepting' and translating reflex radio waves until said interception or translation ceases or reaches a minimum for that location.

5. a The herein described method consisting of electrically balancing a radio wave propagating' and receiving device in a location where the presence of a radio wave reflector is suspected, moving said device along a determined path in respect to said suspected reflector, propagating radio waves at intervals, intercepting and translating radio waves reflecting from said suspected reflector and increasing the manifestations of said waves bymeans of additional currents until 7 said interception and translation stops due to balancing action or reaches a for that location, and thenjmovin said device in a plurality of directions unti said interce tion and translation again stops dueto ancing action or reaches a minimum for that location thereby indicating the approximate location of the reflector.

6. Inthe operation of a looped antenna radio receivingsystem, the method 01E ing reception of radio waves'coming from a given source which consists in-trans the connectionwith each other of two ooped antenna) located at equal distances from the source so that the induced currents are thrown into opposition with each other, and reducing reception of waves coming from a direction at right angles'to the direction of the first waves-by simultaneously rotating the looped antennae as a unit about the source of the first waves as a center.

7. The method ofdetermining the location ing radio waves, which consists in propagating radio waves, substantially balancing two wave-receivin devices at opposite sides of the source of t e propagated waves, reducing direct reception from this source by opposing the currents directly induced in the wavereceiving devices, and rotating the wave-reof a metal or other mass capable of returnceiving devices as a'unit aboutthe source as a center to determine. the position of minimum reception of waves returnedfrom the 7 mass.

8. In the radio receivin system, the method of reduc-' ing the mani estations of radio waves received from a known source which consists in opposing the energies'developed by the currents induced in each of two looped antenoperation of a looped antenna.

nee located at substantially equal distances from this source, and reducing the manifestations of waves received from a direction at an angle to the direction of the first waves b rotating the looped antennae as a unit about the source of thefirst waves as a center.

9. The herein described method of locating masses capable-of returning wireless waves consisting inpropagating wireless waves, from a source positioned in a location wherethe presence of-the mass is suspected, and electrically balancing a wireless wave receivingdevice with respect to direct waves from the source, intercepting and translating reflex wireless waves returned from said mass, until said interception and translation stops or reaches a minimum for that 'spot due to bal-- ancing action, and thensuccessively moving said receiving device in a plurality of directions and repeating the balancing operations in each successive position until said interception and translation again stops or reaches a minimum for that spot. 7

10. The herein described method oflocatmg -capable of returning waves consisting v in propagat ng. waves from a source ositioned 1n a location v where the presence 0 the mass is suspected,

and electrically balancing a wireless wave receiving device with respect to d1rect. waves from the source increasing the mamfestations of receive waves by means of additional current, intercepting and translating reflex wirelesswaves returned from said mass,

until said interception and translation stops or reaches a minimum for that particular location dueto balancing action,-moving the receiving device to a new position in the approximate direction of the mass as thus determined, and repeating the balancing operations in the new position. I 11..The herein described method of locating masses capable o t returning wireless waves consisting in propagating. wireless waves from a source ositioned in a location where the presence oi themass issuspected, and electrically balancing a wireless Wave receiving device with respect to direct waves from the-source, increasing the manifestations of received waves by means of additional current, intercepting and translatin reflex wireless waves returned from sai mass, balancing the receiving device with respect to these intercepted waves to determine the approximate direction from which the reflex waves are received, moving the receiving device in this determined direction to a new position, and repeating the balancing operations in the new position.

12. The herein described method of locat ing masescapable of returning wireless waves consisting in moving a wireless wave circuit having balancing properties in the presence of an operating wireless wave propagating circuit, increasing the manifestations of received waves by means of additional current, balancing out direct propagated waves or waves resulting therefi'om, and receiving and translating wireless waves or manifestations thereof sent out from the mass as a result of the propagated waves.

13. In methods of finding masses by means of wireles waves, the steps of intercepting and balancing out/interfering waves or manifestations thereof, and then intercepting and balancing out waves or manifestations thereof coming frointhe mass, so as to determine the approximate direction of the mass.

14. In methods of finding masses by means of wireless waves propagated from a known source, the steps of interceptin wireless waves and successively suppressing y balancing action the manifestations of waves from the known source, and then of-reflex waves returned from the mass.

15. In methods of finding niasses by means of wireless waves, operating a wireless wave propagating circuit, 0 rating a wireless wave receiving circuit t at is exposed to the angle of reception, and noting pagated waves or'wavee a own mass under conditions in which these waves aredeliminahgl orththeit sup resse ,lncreaslng B. i rece ived waves by means of additional rent, then intercepting and n M waves from an unhownmassand v cmg the receiving circuit partially suppres manifestations of these latter waves. 16. In methods of finding means of wireless waves, operating a wireless wave propagating circuit, 0

M a wave receiving circuit t expand t e propagated waves or waves returned from a known mass, positioning said cir-.v cuit so'that these waves areeliminated or their manifestations suppressed, and vthen making observations by means of said receiving circuit to determine if reflex waves" from an unknown-mass are being 17. In methodsof finding masses by means of wireless waves, operating a 'wirelw wave propagating circuit, 0 a wave receiving propagated waves or waves returned from a known mass positioning said receiving circuit so that tliese waves are eliminated or their manifestations SuppreSed, making observations by means of said circuitto determine if reflex waves from "an unknown mass are being received, and by balancing action the approximate direction from which these latter waves are received.

18. In, methods of finding muses by means i of wireless waves, operating awirelw wave propagating circuit, intercepting and translating reflex waves returncd'irom the mass and received in acircuit having balancing characteristics,increasing the manifestations of received waves by m eams'of additional cur-V m mine the direction of the source of these reflex waves; v

20. In methods of finding a mass by means of wireless waves, operating a =1 wave propagating circuit, operating a wirelm wave receiving device that increases manifestattions of received waves means of addi: tional current. and is towaves propagated from the said circuit or radiated from an object whose location is known, said receiving device beinginapositioninwhidnifno ll tisexposedtothe said mass is present, manifestation of said waves is at a minimum for that particular spot, there observing reception above the said minimum, and moving or rotating the said receiving device until manifestation of waves is at a minimum for that particular spo't,

therebyfinding the said mass.

. line of direction of wave travel is indicated thus indicating the general direction of the said mass.

22. The method consisting in propagating waves, balancing out these waves or waves resulting therefrom, so that they are not manifest or are at least below the maximum for that spot, in a receiving apparatus capable of increasing the manifestations of these waves,- and then in the same rece1v1ng apparatus re-' ceiving and translating reflex waves.

23. In searching methods, operating an electric circuit, intercepting two sets of waves havingthe1r primary power source in the said circuit, suppressing manifestation of one of the said sets of waves bv a balancing method,

translating, and manifesting the other said set of waves or waves resulting therefrom, thereby indicating the presence of an object.

24.6111 methods of locating a ,mass, operating a wave-propagating device whose location is known, thereby causing the said mass to radiate waves which commingle with waves from the said propagating device, intercepting the thus commingled waves, translating and" manifesting them or waves resulting therefrom, maneuvering or rotating the intercepting device until, due to direction-finding action, whereby the general direction of wave travel is indicated, manifestation of waves reaches a minimum for that-particular spot. thereby finding an indicated general line of wave travel under conditions caused by or as may be changed from the normal by the presence of the said mass, thereby indicating the general direction of the latter.

sulting therefrom, so that they are not manifest, or are at least below the minimum for that spot, intercepting reaction waves coming from or caused by the presence of, an object, translating them, and by utilizing additional current manifesting said waves, or waves resulting therefrom, thereby indicating the presence of an object.

27. In methods of searching for masses by means of wireless waves, operating a wireless wave propagating circuit, operating a wireless wave receiving circuit capable of increasing the manifestations of received waves by means of additional current, and balancing said receiving circuit in positions in which direct propagated wave reception from a known source iseliminated or their'manifestations suppressed, and then making observations by means of said receivingcircuit to determine if waves from an unknown source are being received.

28. In methods of searching for masses by means of wireless waves, operating a wavepropagating circuit whose location is known, operating a wave receiving eircuitcapable of increasing manifestations of received waves by means of additional current and making observations by means of said receiving circuit to determine if waves from a mass whose location it is desired to determine are being received, said waves being caused automatically by the said operation of the propagating circuit, and if so, determining by balancing or radio direction finding methods, the approximate direction from which the said waves from a mass are being received, thereby locating the mass.

25. In almethod of finding an object by means of waves, the steps of intercepting and balancing out interfering waves or manifestations thereof, and then intercepting waves coming from, or reaction waves caused by the presence of, the said object, translating them and utilizing additional current to-increase the manifestations of these waves or waves resultingtherefrom, thereby locating the said object.

26. In a finding method, operating an electric circuit intercepting certain waves therefrom, balancing out these waves or waves re- 

